The vast majority of psychological studies recruit test subjects who are Western, Educated, Industrialized, Rich and Democratic – or "WEIRD." Which is... well, weird, given that these people represent a very small segment of the global human population, from a cultural standpoint. Reasons why psychometric testing is just bullshit.
More than ONE full YEAR of Leveled Reading Passages (Nonfiction) that correlate EXACTLY with Social Studies standards!! All the way from the Age of Exploration - Native Americans - American Revolution - U.S. Government - Abolitionists - Civil War - Reconstruction - Westward Expansion - Industrial Revolution - Prosperity & the Great Depression - World War I - World War II - Cold War - Civil Rights - Globalization - Popular Culture Today - WOW!